A delay line may be used to introduce a phase shift for signals propagating on a transmission line. The shift may be controlled to satisfy the requirements of various applications. In order to ensure the wideband integrity of a phase-shifted signal, a low group-delay deviation is required. Well-designed pairs of networks are necessary to guarantee the same phase slope at different delay times over a wider frequency range
There exist a number of strategies designing and connecting pairs of multiple networks with all-pass character. In addition to multistage all-pass structures, the most frequently used are certainly the switching between high and low pass and coupled lines with the principal functionality of the Shiffman coupler. In one type of semiconductor delay line switch structure, serial switches handle the connection of the delay specific lines. An input and output switch is typically used to connect one of the paired structures. Especially for high power, the losses of one switch only will be in the range of 0.5 dB (1 dB/per delay cell) and in multi-phase-shift application the number of serial connected switching cells determine the overall loss.
It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.